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Purification and properties of phosphofructokinase from Dictyostelium discoideum

O H Martínez-Costa1, A M Estévez, V Sánchez

  • 1Departamento de Bioquímica de la UAM, Facultad de Medicina de la Universidad Autónoma, Madrid, Spain.

European Journal of Biochemistry
|December 15, 1994
PubMed

Insights

This study purified phosphofructokinase (PFruK) from Dictyostelium discoideum, revealing a unique homotetrameric structure and distinct biochemical properties compared to other eukaryotic PFruKs.

Area of Science:

  • Biochemistry
  • Molecular Biology
  • Enzymology

Background:

  • Phosphofructokinase (PFruK) is a key glycolytic enzyme.
  • Understanding PFruK from diverse organisms like Dictyostelium discoideum provides insights into enzyme evolution and regulation.

Purpose of the Study:

  • To purify and characterize phosphofructokinase (PFruK) from the slime mold Dictyostelium discoideum.
  • To compare its biochemical properties with PFruKs from other eukaryotic sources.

Main Methods:

  • Purification to homogeneity using multiple steps.
  • Sodium dodecyl sulfate/polyacrylamide gel electrophoresis (SDS-PAGE) for molecular mass determination.
  • Gel filtration for native molecular mass determination.
  • Antibody generation and immunoprecipitation assays.
  • Determination of isoelectric point (pI), pH optimum, and activation energy (Ea).
  • Analysis of amino acid composition.
  • Enzyme kinetics studies and allosteric effector screening.
  • Thermal denaturation assays and phosphorylation studies.

Main Results:

  • PFruK was purified 15,000-fold with 29% yield.
  • SDS-PAGE showed a single 95 kDa subunit; native mass indicated a homotetramer (382 kDa).
  • An antibody raised against Dictyostelium PFruK did not cross-react with yeast or mammalian PFruKs.
  • Apparent pI was 6.8, pH optimum 7.6, and Ea 29.1 kJ/mol.
  • Distinct amino acid composition noted (high Ser, Gly, Glx; low Ala, Val, Tyr).
  • Enzyme kinetics showed no sigmoidal saturation for fructose 6-phosphate and mild MgATP inhibition at acidic pH.
  • Insensitive to typical allosteric effectors but binds fructose 2,6-bisphosphate.
  • Phosphorylation by cAMP-dependent protein kinase did not alter activity.

Conclusions:

  • Dictyostelium discoideum PFruK exhibits unique structural and regulatory properties.
  • These characteristics differentiate it from other known eukaryotic PFruKs, suggesting specialized metabolic roles.
  • Further investigation into the metabolic significance and structure-function relationship is warranted.

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